Concentric gas lift valves



Sept. I19, 1967 E.v D. MCMURRY ETAL 3,342,202

CNCENTRIC GAS LIFT VALVES Filed oct. g, 1964 5 Sheets-Sheet 1 Eve/'eff McMya/rg BY fj I wwy@ Sept 19, 1967 E. D. MCMURRY x-:TAL 3,342,202

CONCENTRIC GAS LIFT VALVES Sept 19, 1967 E; D MGMURRY ETAL 3,342,202

CONCENTvRIC GAS LIFT VALVES Filed oct. 1964 v 5 sheets-Sheet s United States Patent() 3,342,202 CONCENTRIC GAS LIFT VALVES Everett D. McMurry and Bolling A. Abercrombie, Houston, Tex., assignors, by direct and mesne assignments, of one-half to said McMurry and one-half to Knud I. Bruuu, both of Houston, Tex.

Filed Oct. 9, 1964, Ser. No. 402,831 24 Claims. (Cl. 137-155) This invention is concerned with promoting the ow of liquid from wells. It relates to the so-called gas lift art, by which is generally meant the injection of gas under pressure into the production conduit of a well in order to facilitate the flowing of the well Huid, commonly oil, to the surface. This technique is usually used when the formation pressure is insuiiicient to force the Well fluid to the surface, yand eliminates the necessity of providing expensive pumping equipment.

The gas used may be any gas such as air, nitrogen, or hydrocarbon gases; but for safety reasons a gas that will not support combustion is preferred when available.

More particularly, this `invention relates to the gas lift valve in the gas lift system. This is the valve which is inserted in or on the producing conduit and through which the gas is introduced into this conduit. It is this valve which 'affords fluid communication between the producing conduit and the pressurized gas. This communication may be either intermittent, or as design criterion may demand, essentially continuous within limits.

The pressurized gas is conducted through what is herein called the gas injection conduit. In the typical situation, this is the annulus between the well casing (or, if there is no casing, the borehole) and a string of` production tubing suspended therein which constitutes the production conduit. On some occasions, however, an engineer may desire to produce the well fluid from this annulus; on such occasions the tubing is used as the gas'injection conduit.

For purposes of this explanation, however, it Will be assumed that the well'uid being produced is oil and it is being produced through the tubing by means of gas supplied through the annulus, even though it will be understood thatY the invention is useful for producing other fluids and for producing through either conduit.

The gas lift art continues to be burdened with a number of problems. The solutions available to some problems beget other problems of equal stature, and a reasonable combination of problem solutions hasoalways been elusive. For exemple:

In the past a most commonly used and highly preferred gas lift valve assembly, because of its many excellent qualities, has been the ball-and-seat valve (which term is used to include conical, dart, disc, etc. type valve closure members) wherein the opening and closing movement is generally in line with the fluid How rather than across the iluid flow as in sleeve valves. Andy such valve-closures together with related urging means such as pressure responsive devices, have been built upon a chassis secured to the outside of the tubing string `(e.g. King 2,339,487; Walton 2,385,316; Carlisle et al. 2,465,060; Garrettet al. 2,519,242; Garrett et al.` 2,620,741) or to one side of the tubing string (e.g. McGowen et al. 2,679,903 andV Howard et al. 2,664,162).

nIn :all such `arrangements the movement of the valve closure means, and of the pressure responsive urging means, has been oriented parallel to the tubing, and have been produced rather extreme eccentric protrusions to one side of the tubing axis, normally greatly in excess of tubing collar diameter. Such eccentric structures inhibit convenient running of parallel tubing strings in multiple completed wells, hinder running of wash-over 3,342,202 Patented Sept. 19, 1967 tools and conduct of well-cleaning operations in the event of paraffin formation or sand deposits in the Well Some valves currently on the market, known as eccentric-concentric valves, have the gas lift valve chassis of minimized size located close against or in one tubing wall, with the tubing conduit moved eccentrically to the opposite side, wherein the tubing conduit itself is placed out of alignment with the tubing string.A Such arrangements while partially solving the problem of exterior protrusions, do it at the expense of small valve capacity and interior obstructions that inhibit use of certain tools within the string.

Some have solved the acute problem of eccentric protrusions by going to interior valves. Such a valve is illus1 trated in Za'ba 2,633,086 who :also shows exterior protrusions, and in Boynton 2,262,752, Lamb et al. 2,268,041,

Vincent 3,016,844. But the elimination of the exterior protrusion has totally clogged the tubing interior against the running `of tools and has also inhibited fluid flow.

The Thomas 2,317,121 and Re. 21,998 patents both represent interesting failures to solve the problem though he discloses both interior and exterior pressure responsive gase lift valves with radially moving diaphragms.

Other efforts `at solving the problem of how to get a large capacity valve, with the entire assembly being concentric with the tubing string and offering no major protrusions or obstructions either inside or outside the tubing, are represented by Cummings 2,642,889, Archer 1,687,317, and an unpatented structure recently'offered by one company wherein a metal valve seat ran all the way around the entire circumference of the tubing.

The grossly-oversized metal valve seat failed in part because such extremely large seats and cooperating valve closures could not within reasonable cost be machined to adequately close tolerances to seal properly. The sleeveA `Cummings a roach has eno ed some si nificant com-- mercial success, but it suffers a number of disadvantages such as being an inherently balanced valve having no sprea between opening and closing pressures, a valve with high throttling characteristic, and a valve dependent for life upon constantly flexing elastomeric materials used as moving parts operating in high temperature and pressure conditions, with the result of service diiculties and short service life. The commercial success that the Cummings valve has enjoyed, and the strained eiort represented by the valve seat`of the full annular dimension of the production tubing, both dramatize the extreme industry thirst for a Valve assembly affording the advantages of 'the reliable ball-and-seat valve with no major eccentricities or obstructions either inside or outside the tubing.

Further, in most gas lift installations it is desirable-tonecessary to provide not only the gas life valve for controlling gas admission to the production conduit, but also a check valve for preventing ilow in the opposite direction' responsive and valve closure means are preferably eachl mounted directly on tubing wall and oriented for movement in directions perpendicular to the axis of the tubing string rather than parallel thereto as in every commercially significant valve in the past except Cummings, and wherein the'advantages of the metal ball-and-seat and pressure responsive valve are realized in a concentric arrangement compelling no exterior protrusion significantly beyond tubing collar size-though of course any larger exterior protrusion may be utilized in installations where it can reasonably be tolerated.

Another object of this invention is to provide an improved valve structure admitting to one modification which opens in response to both tubing pressure and casing pressure, but closes independently of tubing pressure, and at the same time admitting to another modification that closes at least partly in response to tubing pressure.

Other objects and preferred features are apparent from the following description and accompanying drawings, wherein:

FIGURE 1 is a scrematic elevational view, partly in section of a Well bore having a conduit and valves therein, illustrative of one embodiment of the present invention.

FIGUR-E 2 is a schematic vertical section in detail, illustrating one valve constructed `in accordance with a preferred embodiment of this invention.

FIGURE 3 is an enlargement of one portion of FIG- URE 2, showing the valve seat and valve member in greater detail.

FIGURE 4 is a schematic cross section along line 4-4 of FIGURE 2, showing the FIGURE 2 valve in open position.

FIGURE 5 is also a schematic cross section, taken along line 4-4 of FIGURE 2 and showing that valve in the closed position.

FIGURE 6 is a schematic vertical section of another embodiment of this invention wherein two valves are connected to a single pressure volume chamber.

FIGURE 7 is a schematic vertical section in detail, showing another valve constructed in accordance with an embodiment of this invention.

FIGURE 8 is also a schematic vertical section in detail, illustrating still another valve constructed in accordance with another embodiment of this invention.

As previously suggested, this invention, as illustrated in FIGURE 1, has special application to production of oil or the like from a producing formation 1, through a well borehole 2 by means of pressurized gas. Conveniently, the borehole 2 may be lined with a casing 10 throughout all or part of its depth.

Accordingly, production conduit means are provided in the borehole 2, as by a string of production tubing 3 dening a production conduit 4 extending from the producing formation 1 into communication with an eduction pipe 5 at the surface of the ground. Means may similarly be provided for isolating the annulus 6 between the casing 10 and tubing 3, from the producing formation 1, as for example a packer 7.

Means are provided for supplying a gas under pressure to the annulus 6, for use in ejecting .the oil to be produced. Conveniently, a source of gas under pressure may be connected through a choke or the like, by means of a pipe 9 at the surface, to the annulus -6 which constitutes a gas injection conduit.

And means are provided, preferably at spaced points along the production tubing for passing gas from the gas injection conduit 6 into the production conduit 4. In accordance with the illustrated embodiment, such means take the form of one or more valves 8, 8 located at spaced points which are xedly built upon a housing constituting a short length or portion of the production conduit itself, and not materially projecting into or obstructing either the annulus 6 or the production conduit 4.

THE EMBODIMENTS OF FIGURES 2-5 AND 6 A preferred form of such a valve 8 is illustrated in enlarged elevational section in FIGURE 2 wherein the housing of the valve is seen as tubular member 11 secured at each end to further portions of the production tubing 3. The valve housings box end is illustrated at its upper end, with its pin end secured into tubing collar 12.

In the typical well, the tubing couplings form a tubing collar 12. In one preferred form of valve constructed in accordance with this invention, the outside diameter of the valve tubular housing 11 is approximately the same as the outside diameter of the tubing coupling 12.

Fixedly mounted in and/ or directly upon the walls of said tubular housing 11, are the various operating parts of the valve assembly illustrated, namely: A valve seat member 13, having therein a valve seat 14 defining a valve port 15; a valve closure means 17 abuttingly engageable with a linkage means 24 which is in turn abuttingly engageable with a pressure responsive source 1S of force to actuate the assembly.

The valve and seat assembly The valve in fully open position is illustrated in FIG- URE 4; the valve in closed position is illustrated in FIG- URE 5; an enlarged detail of the valve and seat assembly is shown in FIGURE 3.

Most conveniently there is mounted in the wall of the tubular housing 11 a valve seat member 13 which constitutes or has mounted therein the seat 14. The valve seat 14 defines a valve port 15 which affords fluid communication between the production conduit 4 and (through holes 16) the gas injection conduit 6.

In the side walls of said seat member 13 are provided a series of small openings 23 out of which gas may pass when the valve is open (FIG. 4) to the area 26 immediately inside the wall of the tubular housing 11.

As best seen in FIGURE 3, cooperatingly engageable with said valve seat 14 is a free floating valve closure member 17, of form just in excess of a hemisphere in the embodiment illustrated. Its movements to open and to close the valve are in the general line of gas ow rather than across the gas ow as in sleeve valves.

When on seat 14, valve member 17 closes the valve. When member 17 is off seat 14, gas is permited to pass around its periphery, through openings 23 in the seat member 13 and openings 25 in the linkage member 24 below discussed.

In the embodiments of FIGURES 2-5, the diameter of the valve closure member 17 relates to the inside diameter of the walls of the valve seat member 13, so as to constitute a constriction restricting gas ow past the valve member 17 even when off its seat 14, and creating a major pressure drop at that place and the exit holes 23 constitute more constriction than inlet holes 16 or the valve seat when the valve is open.

Accordingly, the spherical side of the valve member 17 remains exposed to annulus gas injection pressure even when the valve is open, and the flat side of the valve member 17 is exposed to tubing pressure through pressure access holes Y25 provided in the actuator 24.

Accordingly, when valve member 17 is in closed position, the area 14 (See FIG. 3) of valve member 17 (the area 14 corresponding to the area of the valve seat 14) is exposed to the pressure in the gas injection conduit 6. However, when the valve member is in the open position, the portion 17 of the valve member is exposed to the gas injection conduit pressure.

This results in the often very desirable spread characteristic of the valve illustrated, which is inherently absent from the Cummings 2,642,889 and many other valves.

Normal valve opening occurs when annulus pressure is higher than tubing pressure. Hence once the valve commences to open the higher gas injection conduit pressure immediately begins to act over a larger valve area than it did immediately prior to opening, thereby enlarging the force-to-open immediately after the opening commences. Thus, a considerably higher gas injection conduit pressure is necessary to open the valve than is necessary to hold it open, that difference depending upon the difference in area 14 by comparison with area 17.

If it is desired for a given installation to provide a valve without significant spread, this is easily accomplished by providing a valve seat area 14' that is essentially as large as the area 17.

Linkage means Actuator linkage means for transmitting thrust and motion between said valve member 17 and the movable portion 19 of a pressure responsive means hereafter discussed, are provided. In the embodiment of FIGURES 2-6 this actuator linkage member takes the form of a thrust ring 24 best seen in FIGURES 4 and 5, making abutting engagement with each the bellows portion 19 and the inside-tubing side of the valve member 17.

Thrust ring 24 is preferably mounted essentially concentrically with the tubing string, and is just enough larger than the tubing string inside diameter to leave it open and unobstructed even at the extremities of movement of the ring 24. Thrust ring 24 is also enough smaller than the inside diameter of the housing 11, to leave a play or space 26 between it and the housing 11 through .which gas may pass if the designer so desires and in which the ring may move to perform its function.

The thrust ring 24 is also abuttingly engageable with the movable end 19 of bellows 18. Thus forces impressed upon the thrust ring 24 by annulus pressure upon the valve member 17 are transmitted to the bellows; and similarly forces derived from the bellows are transmitted by the thrust ring 24 to the valve member 17.

Check valve feature Y trated in FIGURES 2-6 the valve member 17 closes in the direction against normal gas ow, and either alone or in conjunction with associated parts (like the linkage 24) it is also-free to move as a check valve to preclude backward ow.

Pressure responsive means In `accordance with this invention, some pressure responsive means is provided as a source of closing force forthe valve While in some special applications such means may take the form of a spring, or of a bellows, diaphragm or piston exposed to two ditferent wellderived pressures on opposite sides thereof, in the ernbodiment illustrated in FIGURES 2-6 the pressure responsive means takes the form of a pressure-charged bellows 18.

The location of the pressure responsive means 18 relative to the valve member 17 merits perhaps a comment. The disposition of the pressure responsive means 18 away from the valve member 17, along the surface of the housing, is a most convenient and apparently heretofore unappreciated feature of design in aid of good small-OD concentric valves.

In the embodiment of FIGURE 8 this disposition ist axially along the length of the housing 11. In the embodiment of FIGURES 2-7 it is arcuately around the housing 11. While applicant finds special advantages in locating the pressure responsive means and valve member 180 from each other as in FIGURES 4 and 5, other arcuate dispositions may also be used, particularly when a lever arm type actuator linkage is selected.

Pressure volume chamber Preferably the pressure responsive means is a diaphragm, piston or bellows which is pre-charged on one side thereof with predetermined gas pressure. Any such device tends to increase its resistance to compression as the compression occurs, because its volume is thereby being reduced and the gas therein compressed. This increase in resistance as compression occurs, may be called the spring rate, and the spring rate of small pressurecharged bellows is excessive for most gas lift operations.

Therefore, in accordance with the preferred embodiments of this invention, within the wall of the tubular housing 11 is provided a pressure volume chamber 22 which is in fluid communication through a conduit 21 with the pressure-charged side of the bellows 1S. This chamber 22 may extend all the way around the housing 11,V or part way around as indicated by the dotted lines 22', in order to facilitate easiest construction of a chamber of the desired size.

Contrary to the commercial history of the gas lift art, the pressure volume chamber is located not in line with the movement of the movable portion of the pressure responsive means, but rather to the side of the pressure responsive means in a direction perpendicular to the axis of movement.

The pressure volume chamber is pre-charged through an appropriate opening (not shown) which preferably includes a spring loaded check valve (not shown) not much different from the check valve in common use in the openings for pressurizing automobile and bicycle tires.

Orientation of pressure responsive means Y The orientation of the axis of movement of the pressure responsive means, in combination with other features of this invention, is also of note in that its preferred form represents a departure from all significant commercial history in the gas lift art.

In accordance with the FIGURE 2 embodiment, the bellows 18 has a fixed end 20 mounted fxedly into the tubular housing 11, and a movable end 19 extending inwardly therefrom, so that the movable portion 19 moves in a direction not parallel to, but rather perpendicular to the axis of the tubing string.

This disposition gives rise to one of the design problems that has heretofore precluded the commercial use of ball-and-seat type closures in valve assemblies of coupling size outside diameter, namely the requirement of major dimensions of valve movement to open, which means a relatively long rbellows in bellows-type valves.

The preferred valve of this invention is therefore deliberately designed for small opening movement, by comparison with the prior art valves such as King 2,339,487 and those develomd on the King valve theme; and the large volume of gas is passed with small movement either by using a relatively larger valve diameter, or by using multiple valves as illustrated in FIGURE 6, or both, but in any event without protrusions extending outwardly of the coupling diameter.

In one preferred form illustrated in FIGURE 6, the multiple-valve concept takes the form of a single pressure volume chamber 22, interconnecting both of two or more bellows-actuator-valve assemblies in the same tubular housing 11. This arrangement is preferred for its assurance of simultaneous operation of the valves to afford the quantities of gas flow desired; but a separate pressure system may be used for each bellows-actuator-valve assembly if desired.

Relative size of bellows and valve port The common commercial practice has heretofore been to have a bellows of effective cross sectional area of perhaps 'asquare inch in a typical case, while the valve port is two-tenths of a square inch, i.e. 20% of the bellows area. In such an arrangement, the valve passes volumes of gas through a full-open 20% size port, and when closed it is responsive 20% to tubing pressure and 80% to annulus pressure in determining when to open.

, In accordance with preferred embodiments of this invention, the port size 14 for a comparable operation is selected at of the`bellow`s size, thus exposing as before, 80% ofthe bellows to annulus inuence and leaving 20% exposed to tubing inuence. But the valve port is thereby rendered four times larger than in the previously conventional 20% valve, thus affording a valve that can be opened adequately for the same gas volume as before with an opening movement on the order of 1A as much and a bellows on the order of 1A as long. The larger valve port is thus fully open with less movement.

While metallic diaphragm valves have been heretofore conceived (e.g., Thomas 2,317,121) they have not heretofore proven of commercial importance for todays gas lift practice because interalia, the requirementsfor movement exceeded the movement limits a diaphragm of practical down-well size could reliably provide. Since this invention demands so much less valve movement than prior designs, it is practical by the use of this invention to devise metallic dia-phragm valves for a number of applications.

Valve closing respo-nse in the typical prior-art example selected above, with a King-type valve, is substantially 100% responsive to annulus pressure whenever the 20% port is the main flow construction as is most common. Similarly in accord with this invention, the valve closing response can be rendered substantially 100% responsive to annulus pressure, by selecting the area 17 to be exactly equal to the effective operating cross sectional area of the bellows 18.

Almost any other desirable percent of responsivenesson-closing to annulus pressure, can be obtained by appropriate sizing of the area 17' relative to the bellows effective area. Accordingly one of the teachings of this invention is the predetermination of the percent of responsiveness upon closing annulus pressure, by sizing the effectivewhen-open-diameter of the valve member 17 to be the desired percent of the effective diameter of the bellows.

Operation The operation of the embodiment of FIGURES 2, 4 and 5 may be understood by consideration of an operating example of one useful embodiment of this invention.

The bellows 18 of a valve 27 constructed in accordance herewith is loaded at any desired pressure, and the valve is inserted into the production tubing 3 of an operating well. Gas under pressure is piped into the annulus 6 between the tubing and casing from a gas compressor located at the well head, with suitable apparatus at the surface so that the gas pressure may be adjusted to any desired level. This pressure acts on the valve member 17 across the area 14 of the valve seat, urging the valve to open, whereas the bellows pressure acts in the opposite direction across the area of the bellows. This pressure exerted by the bellows is transmitted to the thrust ring 24 as a force perpendicular to the axis of the tubing. The thrust ring 24 in turn, transmits the force to the valve member 17, urging it closed.

Oil rising in the production tubing also exerts a certain pressure on both the valve member and bellows, depending of course on the height of the column of oil. The pressure of the oil in the tubing may he thought of as split into two components: a` rst component acting against the valve member, urging the valve closed; and a second component acting against the bellows urging the valve open. The net effect of the tubing pressure, therefore, acts only across an area which represents the difference between the area of the bellows and the area of the valve seat.

Assume that the area of the bellows is 1 square inch, the bellows pressure 600 p.s.i., the area of the valve seat is 0.8 square inch, and the area 17' of the valve member may be 0.9 square inch. If the tubing pressure is 300 p.s.i., the casing (annulus) pressure must be raised to 675 p.s.i. before the valve will open. If the tubing pressure is 500 p.s.i., a casing pressure of 625 p.s.i. will be required to open the valve; if 100 p.s.i. tubing pressure, 725 p.s.i. casing pressure is required.

Once the valve is open, however, the casing pressure in our example acts on 0.9 square inch, rather than 0.8 square inch. So, if the tubing pressure remains at 300 p.s.i., the casing pressure must drop to 633 p.s.i. before the valve will close. lf tubing pressure is 500 p.s.i., casing pressure must drop to 611 p.s.i., if pounds tubing pressure, casing pressure must drop toabout 655 pounds. Thus, there is a spread between opening and closing pressure which eliminates the necessity for a surface intermitter and promotes efficient operation in that neither too little nor too much gas is injected into the tubing to lift the slug of oil, then above the valve, to the surface.

THE EMBODIMENTS OF FIGURES 7 AND 8 It is of course apparent that other embodiments may be devised without departure from the scope of some embodiments of the invention.

For example, there is illustrated in FIGURE 7 a concentric valve assembly wherein the valve seat 27 faces outwardly, and the valve member 28 seats going inwardly. There the gas flow :path is upward against the check valve member 29, to blow it to the dotted position 29', so that the gas may then pass through opening 30 into the tubing.

In this embodiment, the pressure responsive means is illustrated as a flexible diaphragm 31, which is loaded by a charge of pressurized gas on the inside of it and in pressure volume chamber 32 which may be pressure-charged through a plug 33. The linkage means between the diaphragm 31 and the valve 28 takes the form of an exterior annular ring 34.

In the embodiment of FIGURE 8, there is again a flexible diaphragm type pressure responsive means 40, pressure loaded by pressure in chamber 41 which is chargeable by means of a removable plug 42. In this instance, the linkage from the pressure responsive means 40 takes the form of a lever arm 43 pivoted at 44 and carrying valve closure member 45 which is adapted to seat on seat 46. In this embodiment a separate check valve 47 is carried on the face of the valve closure member 45.

It is apparent that a curved lever arm, extending partially around the circumference of the tubing, might be used to connect a pressure responsive means and a valve closure member that are perhaps 30 to 180 apart, just as the straight arm works when the valve closure is axially removed from the pressure responsive means.

The foregoing description is illustrative only and does not purport to cover every alternative embodiment or use of the invention. For example, while the invention has been described primarily with respect to intermittent gas flow operations, those experienced in the art readily recognize how to use the invention in continuous-flow operations. Further, while the importance of concentric valves has quite properly been emphasized, some inventive features herein disclosed that are significant to good concentric valve design, are also useful in eccentric valves and are therefore also claimed without restriction to concentricity. Accordingly, the foregoing description should not be construed as any limitation upon the scope of the invention as defined in the following claims.

For convenient reference, the reference numerals used in the foregoing description are set forth below:

l-producing formation Z-borehole 3-production tubing 4-production conduit S-eduction pipe -annulus between tubing and casing 7-packer 8--valve 9-pipe to source of gas under pressure 10casing ll-valve housing 12-tubing collar 13-valve seat member 14-valve seat 14-area of valve member corresponding to area of valve seat 14 IS-valve port 16-holes in valve seat member 13 17-valve closure member 17-area of valve member 17 on which gas injection conduit pressure .acts when the valve member is in open position 19-movable end of bellows 20--iixed end of bellows 21-conduit between bellows and pressure volume chamber l 22-pressure volume chamber 23-openings in valve seat member 24-thrust ring 4actuator linkage 25-holes in thrust ring 26-space between housing 11 and `actuator ring 24 27-va1ve seat 28-valve member 29-check valve member S50- gas flow passage 31-flexible diaphragm `s2- pressure volume chamber 33t-plug to pressure volume chamber 3ft-actuator linkage ring 40-exible diaphragm 41-pressure volume chamber t2- plug for opening to pressure v olume chamber i3-lever arm i t4-pivot of lever 43 to housing 11 45-valve closure member 46-valve seat 47-check valve We claim:

1. In a borehole connected to a source of gas under pressure and containing a string of tubing, a gas-lift apparatus comprising at least one Valve housing generally concentrically interconnected with said tubing string as an integral huid-conducting portion thereof and having at one side a valve seat defining a port interconnecting the interior of said tubing string and the annular space about said tubing string,

a movable valve member for fluid-sealing engagement with said valve seat,

pressure-responsive means spaced arcuately about said Valve housing from said valve seat for movement traversely to the longitudinal axis of said tubing string, and

actuating means disposed arcuately between said pressure-responsive means and said valve member for transmitting movement of said pressure-responsive means to said Valve member traversely of said tubing string axis without substantially impeding fluid flow through said tubing string and valve housing.

2. The gas-lift apparatus described in claim 1, Wherein said actuating member is an annular member disposed generally concentrically about said housing between said pressure-responsive means and said valve seat and valve member.

3. The gas-lift apparatus described in claim 2, wherein said movable valve member is responsive to liquid pressure greater than gas pressure to engage said valve seat independently of said pressure-responsive member and said annular member.

4. The gas-lift apparatus described in claim 2, wherein said movable valve member is responsive to pressure in said tubing string greater than pressure in said annular space to engage said valve seat independently of said pressure-responsive member and said annular member.

5. The gas-lift apparatus described in claim 4, wherein said apparatus further comprises a pressure reservoir dis- 10 posed at the side of said valve housing and interconnected to maintain a preselected internal pressure in said pressure-responsive means.

6. The gas-lift apparatus described in claim 5, wherein said pressure-responsive means is ya bellows disposed in said valve housing for linear expansion and contraction generally perpendicularly to said tubing axis.

7. The gas-lift apparatus described in claim 6, wherein said movable valve member is at least partially exposed on one side to pressure `in said tubing and at least partially exposed on the other side to pressure in said annular space when said valve member is engaged with said valve seat. i

8. The gas-lift apparatus described in claim 7, wherein said movable valve member is more exposed on said other side to pressure in said annular space when said valve member is disengaged from said valve seat than when said valve member is engaged with said valve seat. t 9. The gas-lift apparatus described in claim 8, wherein the area of the valve seat is smaller than the area of said bellows, and

wherein the opening force developed on said valve member by said tubing pressure is functionally related to the difference between the valve seat area and the bellows area.

10. The gas-lift apparatus described in claim 8, wherein said port defined by said valve seat provides ow constriction at a location downstream of said other side of said valve member greater than flow constriction at any location in said port when said valve member is disengaged from said valve seat.

11. The gas-lift apparatus described in claim 5, wherein said pressure-responsive means is a diaphragm disposed in said valve housing for linear displacement generally perpendicularly to said tubing axis.

12. The gas-lift apparatus described in claim 11, wherein said movable valve member is at least partially exposed on one side to pressure in said tubing and at least partially exposed on the other side to pressure in said annular space when said valve member is engaged with said valve seat.

13. The gas-lift apparatus described in claim 12, wherein said movable valve member is more exposed on said other side to pressure in said annular space when said valve member is disengaged from said valve seat than when said valve member is engaged with said valve seat.

t 14. The gas-lift apparatus described in claim 13, wherein the area of the valve seat is smaller than the area of said diaphragm, and

wherein the opening force developed on said valve member by said tubing pressure is functionally related to the difference between the valve seat area and the diaphragm area.

15. The gas-lift apparatus described in claim 13, wherein said port defined by said Valve seat provides flow constriction at a 4location downstream of said other side of said valve member greater than How 4constriction at any other location in said port when said valve member is disengaged from said valve seat.

16. The gaslift apparatus described in claim 15, wherein said valve Ihousing has at one side a first and second valve seats spaced apart longitudinally of said tubing string and each defining a port interconnecting the interior of said tubing string and the annular space about said tubing string,

wherein said pressureresponsive means includes first and second bellows spaced apart longitudinally of said tubing string along said valve housing for expansion and contraction generally perpendicular to said tubing axis,

wherein said pressure reservoir is disposed generally between said iirst and second bellows,

wherein said gas-lift apparatus includes a first movable valve member for fluid-sealing engagement with said first valve seat and a second movable valve member for fluid-sealing engagement with saidsecond valve seat, and f wherein said actuating means includes a irst annular member disposed generally concentrically about said housing between said rst bellows and said first valve seat and first valve member and a second annular member disposed generally concentrically about said housing Ibetween said second bellows and said second valve seat and second valve member.

17. The gas-lift apparatus described in claim 1, wherein said valve member is responsive to liquid pressure greater than gas pressure for Huid-sealing engagement with said valve seat and responsive to gas pressure greater than liquid pressure for disengagement from said valve seat.

18. The gas-lift apparatus described in claim 1, wherein said valve member is responsive to pressure in said tubing string greater than pressure in said annular space for fluid-sealing engagement with said Valve seat and responsive to pressure in said annular space greater than pressure in said tubing string for disengagement from said valve seat.

19. The gas-lift apparatus described in claim 18, wherein said apparatus further comprises actuating means responsive to variations in ambient pressure to maintain said valve member engaged with said valve seat when said ambient pressure is less than a preselected ambient pressure.

in said valve lmember engages said valve seat independently of said actuating means in response to pressure in said tubing string greater than pressure in said annular space.

20. The gas-lift apparatus described in claim 19, where- 21. The gas-lift apparatus in claim 20, wherein said actuating means comprises a pressure-responsive means movable in two directions in response to variations in ambient pressure, and

a valve actuator for urging said valve member into engagement with said valve seat in response to movement 0f said pressure-responsive means in one of said two directions and for moving away from and exposing said valve member to pressure in said tubing in response to movement of said pressure-responsive means in the other of said two directions.

22. The gas-lift apparatus described in claim 21, wherein said valve actuator is movable generally perpendicularly to said tubing axis.

23. The gas-lift apparatus described in claim 22, wherein said pressure-responsive means is a bellows disposed in one side of said valve housing for linear expansion and contraction generally perpendicularly to said tubing axis.

24. The gas-lift apparatus described in claim 22, wherein said pressure-responsive means is a diaphragm disposed in one side of said valve housing for linear displacement generally perpendicularly to said tubing axis.

References Cited UNITED STATES PATENTS Re. 24,015 5/1955 Walton 137--155 X 2,806,429 9/1957 Anderson 137--155 XY 2,904,058 9/19'59 Cummings 137--155 3,183,922 5/1965 Lamb 137-155 ALAN COHAN, Primary Examiner. 

1. IN A BOREHOLE CONNECTED TO A SOURCE OF GAS UNDER PRESSURE AND CONTAINING A STRING OF TUBING, A GAS-LIFT APPARATUS COMPRISING AT LEAST THE VALVE HOUSING GENERALLY CONCENTRICALLY INTERCONNECTED WITH SAID TUBING STRING AS AN INTEGRAL FLUID-CONDUCTING PORTION THEREOF AND HAVING AT ONE SIDE A VALVE SEAT DEFINING A PORT INTERCONNECTING THE INTERIOR OF SAID TUBING STRING AND THE ANNULAR SPACE ABOUT SAID TUBING STRING, A MOVABLE VALVE MEMBER FOR FLUID-SEALING ENGAGEMENT WITH SAID VALVE SEAT, PRESSURE-RESPONSIVE MEANS SPACED ARCUATELY ABOUT SAID VALVE HOUSING FROM SAID VALVE SEAT FOR MOVEMENT TRAVERSELY TO THE LONGITUDINAL AXIS OF SAID TUBING STRING, AND ACTUATING MEANS DISPOSED ARCUATELY BETWEEN SAID PRESSURE-RESPONSIVE MEANS AND SAID VALVE MEMBER FOR TRANSMITTING MOVEMENT OF SAID PRESSURE-RESPONSIVE MEANS TO SAID VALVE MEMBER TRAVERSELY OF SAID TUBING STRING AXIS WITHOUT SUBSTANTIALLY IMPEDING FLUID FLOW THROUGH SAID TUBING STRING AND VALVE HOUSING. 